Scanning electron microscope

Abstract

In a scanning electron microscope, slimming is reduced by reducing a frame count. As the frame count is reduced, the amount of detected secondary electrons decreases, so that a probe current amount is increased to emit an increased amount of detected secondary electrons. A primary electron beam is scanned on a sample, a histogram is created, and the histogram is second-order differentiated to calculate a level of halftone at which a sample image changes in contrast, and to calculate the probe current amount. By adjusting the frame count suitable for the calculated probe current amount, and the contrast suitable for the sample image, the slimming of the sample is limited, and a highly visible sample image is generated for length measurement.

Description

BACKGROUND OF THE INVENTION[0001]The present invention relates to a scanning electron microscope for observing a miniature pattern to measure dimensions thereof, and more particularly, to a scanning electron microscope for observing and measuring a sample, the shape of which can be deformed by an electron beam irradiated thereto.[0002]Scanning electron microscopes (SEM) are widely used in manufacturing and testing steps of a functional product such as a semiconductor device, a thin film magnetic head, and the like, which are fabricated by micro-machining the surface thereof, for measuring widths of processed patterns and inspecting the appearance of resulting products. The scanning electron microscope is an apparatus for forming the image of a sample by narrowing down an electron beam emitted from an electron source with a converging lens or an objective lens which makes use of an interaction of a magnetic field or an electric field with the electron beam, one-dimensionally or two-d...

AI Technical Summary

Benefits of technology

The present invention provides a scanning electron microscope that can reduce the influence of slimming when observing or measuring samples, such as ArF resist, that are vulnerable to electron beam irradiation. By reducing the frame count and increasing the probe current amount, the microscope can detect an increased amount of secondary electrons emitted from the sample, ensuring an image quality equivalent to a sample image generated by a conventional method, even though the frame count is reduced. The invention also includes a control processing unit that creates a luminance histogram, controls the current value of the primary electron beam, and controls the amplifying condition for the amplifier to provide optimal contrast and brightness for the sample image. Overall, the invention improves the quality and efficiency of scanning electron microscopy for various applications.

Problems solved by technology

However, the results of recent investigations have revealed that the ArF resist is highly vulnerable to electron beam irradiation, and when a formed pattern is observed or measured with a scanning electron microscope, the scanning of a converged electron beam causes a condensation reaction in a base acrylic resin or the like, resulting in a reduction in volume (hereinafter called “slimming”) and an eventual change in the shape of a circuit pattern.

However, a reduction in the irradiation density of an electron beam causes a reduction in the amount of secondary electrons generated from the sample, resulting in a dark image.

Disadvantageously, the prior art method of reducing the slimming does not take into consideration an image control technique which relies on the relationship between the number of times of electron beam scanning required for creating a sample image (hereinafter called the “frame count”) and the probe current amount, and fails to sufficiently reduce the slimming and generate a highly visible sample image.

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